Blender reverses X-axis when exporting Z-forward
You cannot export to left-handed system in Blender (not with default 'orientation toolkit' used by most exporters at least). As @sambler said, this only performs rotations (and uniform scaling).

Note that switching something as complex as a Blender scene from right to left handed coordinates is a nice little nightmare (think about animations, parenting, etc.), afaik nobody ever seriously worked on this topic so far.